Preheat your oven to 180°C (350°F). Grease two 23cm (9-inch) round cake pans and line the bottoms with parchment paper. Gather your ingredients so they're ready to go.
In a large mixing bowl, whisk together the flour, sugar, baking powder, and a pinch of salt until well combined. This creates a light, even dry mixture for your sponge.
In another bowl, beat the eggs, vegetable oil, vanilla extract, and buttermilk until smooth and slightly frothy, about 2 minutes. This forms a rich, fragrant wet mixture.
Pour the wet mixture into the dry ingredients and gently fold until just combined. Be careful not to overmix; the batter should be smooth and slightly elastic.
Divide the batter evenly between the prepared pans and smooth the tops with a spatula. Tap the pans lightly on the counter to remove air bubbles.
Bake in the preheated oven for 25-30 minutes, until the cakes are golden and a skewer inserted in the center comes out clean. Cool the cakes in their pans for 10 minutes, then transfer to a wire rack.
While the cakes cool, hull the strawberries and blend them until smooth. Pass the puree through a fine sieve to remove seeds, resulting in a silky, vibrant red liquid.
In a stand mixer or with a hand whisk, beat the softened butter until fluffy and pale, about 3 minutes. Gradually add the sifted powdered sugar, beating after each addition until fully incorporated and smooth.
Add 2-3 tablespoons of strawberry puree, a teaspoon of lemon juice, and vanilla extract to the butter mixture. Beat again until the frosting is vibrant pink, smooth, and creamy.
Place one cake layer on a serving plate. Spread a thin layer of strawberry buttercream on top. Place the second layer over it and apply the remaining frosting evenly over the top and sides of the cake.
Decorate with fresh strawberries or other toppings as desired. Chill the cake in the fridge for at least 30 minutes to set the frosting before slicing and serving.
